Baltimore County fire crews sent 11 engines, tankers and other equipment to the scene. In addition to firefighters at the scene, a State Highway Administration crew with a front-end loader was among the equipment being used to clear the highway.

SkyTeam 11 reported traffic delays approaching the area extending 10 miles into the Towson area. The left shoulder was getting by the scene shortly after 11:45 a.m. The clean-up took more than two hours to ensure the roadway was safe for traffic. By 2 p.m., the two left lanes were re-opened. All lanes re-opened by the evening rush hour.

Drivers stuck in the traffic jam for hours may have enjoyed an otherwise sunny winter day with temperatures in the upper 70s -- despite the delays. State police continue to investigate a cause.

"We certainly hope it wasn't a careless cigarette thrown out of someone's window into that load of straw, but that is a possibility. We have no evidence of that right now," state police spokesman Greg Shipley said. "With weather like this, straw just doesn't start burning all of a sudden."

Commuters on the Beltway flagged the driver of a heavy duty pickup truck pulling a trailer load of 464 bales of straw that the load was on fire, state troopers said.

No injuries were reported.

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